The invention relates to an apparatus for loading and unloading disk-shaped substrates into and out of a vacuum coating chamber through airlocks and for transporting the substrates within this chamber, having at least one station for loading and unloading and at least one coating station, at least one lifting means and at least one rotatably mounted substrate holder, as well as a motor for operating the lifting means and the substrate holder.
In vacuum processing technology, especially in the thin-coating technology, the coating of substrates, such as compact disks (CD's) is well-known. These disk-shaped substrates are used widely as a means for storing digital data. In a sputtering process, the stamped plastic disks are covered with an aluminum coating. The sputtering apparatus used for this purpose have, in many cases, a turntable for transporting the substrates.
A rotating arm transports the substrates from a buffer of a handling system into the vacuum chamber. In the chamber the substrates are placed on a turntable and transported by the latter through the individual stations in the vacuum chamber. Usually at least two stations are provided in this chamber. These are a loading and unloading station, and a coating station.
U.S. Pat. No. 4,820,106 discloses an apparatus for loading and unloading a substantially flat workpiece into and out of an evacuated coating chamber through an airlock and for shifting the workpiece in and out of the range of the coating source for the purpose of treating the workpiece surface.
Also known is an apparatus of the kind in question (U.S. Pat. No. 3,874,525) which has a coating chamber in which a two-armed pick-up tool is mounted for rotation about a vertical axis. At its diametrically opposite extremities this two-armed pick-up tool has forks, which can be moved toward and away from one another in a vertical plane by means of a rack drive with motor. In another document (DE 39 12 295) a cathode sputtering apparatus for coating substrates in a vacuum chamber is described, in which a rotating substrate holder is housed, having at least one cathode station, and a loading and unloading station, the substrate holder including at least one transport tray.
To set these transport trays in a rotating movement it is proposed that, for one or more trays, a driving means centrally disposed with respect to the cathode sputtering apparatus be provided which advances the transport tray in the vacuum chamber in steps of a certain angular amount.
All these known apparatus have the disadvantage that the individual movements are performed by individual driving means. For example, for the raising and lowering of the swivel arm disposed in front of the chamber and for the raising and lowering of the substrate plates within the chamber, individual pneumatic cylinders are used. For the rotation of the swivel arm and turntable, electric motor drives, for example, are provided.
For the coordination of the individual movements a number of individual signals are necessary, which are accessed and operated through a system-programmable control. To process the individual signals a corresponding delay is necessary, in which no movements of the driving means can be performed. This in turn has a disadvantageous effect on the total length of the coating cycle. Since the apparatus in question are used exclusively for the coating of large quantities of substrates, and are usually run in three shifts, the cycle length is of considerable economic importance.